Search

This study investigates heterogeneity in the deformation of an annealed sheet of commercially pure titanium (cp-Ti), its variation with loading direction and its influence on dwell fatigue response. Cp-Ti sheet with a typical cold rolling texture was deformed, along its rolling direction (RD) and transverse direction (TD), to the same strain level in tension. Higher level of grain boundary sliding in TD led to increased surface roughness (30% higher) in TD when compared to RD. Whereas, the higher extent of grain boundary-affected zones in TD resulted in a higher level of strain gradient, as evident from higher Kernal Average Misorientation values observed in TD. The reason for the higher extent of grain boundary sliding and formation of grain boundary-affected zones in TD samples was higher compatibility issues in TD. This work proposes a criterion defining the compatibility of a boundary. This criterion, which is based on the c-axis deviation of constituent grains with respect to the loading axis and the geometric compatibility of slip systems, is demonstrated to define the compatibility of a boundary completely. Using this criterion, a higher fraction of incompatible boundaries is identified in TD. Moreover, the markedly superior dwell fatigue response of RD samples when compared to TD is partly attributed to the lower heterogeneity in the nature of deformation in the former. Furthermore, textures with less damage prone grain boundaries and hence better dwell fatigue resistance is also proposed. Taken together, the present work underlines the principal role of crystallographic texture on the mechanical behaviour in general and dwell fatigue in particular. [ABSTRACT FROM AUTHOR]